Prismatic sealed secondary battery

ABSTRACT

The positive electrode substrate exposed portions or the negative electrode substrate exposed portions, or both, of an electrode assembly is split into two groups, and therebetween is disposed an intermediate member made of a resin material and holding one or more connecting conductive members. Collector members for the substrate exposed portions split into two groups is electrically joined by a resistance welding method to the substrate exposed portions split into two groups, together with the connecting conductive member(s) of the intermediate member. The resin material portion of the intermediate member protrudes, in the extension direction of the substrate exposed portions split into two groups, beyond the ends of the substrate exposed portions split into two groups and the ends of the collector member to a prismatic outer can. This structure enables enhanced resistance between the substrate exposed portions and the collector member and curbs variation in the welding strength.

This application is a continuation of U.S. application Ser. No.14/599,007, filed on Jan. 16, 2015, which is a continuation of U.S.application Ser. No. 13/192,292, filed on Jul. 27, 2011, now U.S. Pat.No. 8,968,914 issued on Mar. 3, 2015, which claims priority to Japanesepriority application No. 2010-170551 filed on Jul. 29, 2010, theentirety of both being hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a prismatic sealed secondary batterythat has stacked positive electrode substrate exposed portions andnegative electrode substrate exposed portions, in which at least one ofthose sets of substrate exposed portions is split into two groups,connecting conductive members are positioned and disposed between suchtwo groups, and the substrate exposed portions are resistance-welded tocollector members and to the connecting conductive members, so thatlowered resistance and stabilized quality of the welds are realized.

BACKGROUND ART

With the rise of the environmental protection movement over recentyears, restrictions on emissions of carbon dioxide and other exhaustgases that cause warming have been strengthened. Consequently, theautomobile industry is engaging actively in development of electricvehicles (EVs), hybrid electric vehicles (HEVs) and the like, to replacevehicles that use fossil fuels such as gasoline, diesel oil and naturalgas. As the batteries for such EVs and HEVs, nickel-hydrogen secondarybatteries or lithium ion secondary batteries are used. In recent years,nonaqueous electrolyte secondary batteries such as lithium ion secondarybatteries have come to be used in large numbers for this purpose,because they provide a battery that is both lightweight and highcapacity.

EVs and HEVs are now required not only to be environment-friendly, butalso to have basic performance as vehicles, that is, accelerationperformance, gradient-climbing performance, and other high-level drivingcapabilities. In order to satisfy such requirements, batteries areneeded that have not simply an enhanced battery capacity but also highoutput. The secondary batteries widely used for EVs and HEVs usually areprismatic sealed secondary batteries in which a generation element ishoused inside a prismatic outer can, and the internal resistance of suchbatteries must be reduced to the extent possible, because large currentflows in them when high-output discharge is performed. For this reason,various improvements have been undertaken concerning lowering theinternal resistance by preventing welding faults between the electrodeplate substrates and the collector members in the generation element ofthe battery.

There exist the methods of mechanical caulking, welding, and so forth,for electrically joining the electrode plate substrates and thecollector members so as to effect electrical collection in thegeneration element. For electrical collection in batteries that arerequired to have high output, welding is the appropriate method, sinceit is likely to realize lower resistance and unlikely to deteriorateover time. In lithium ion secondary batteries, aluminum or aluminumalloy is used as the material for the positive electrode platesubstrates and collector members, and copper or copper alloy as thematerial for the negative electrode plate substrates and collectormembers to realize lower resistance. However, aluminum, aluminum alloy,copper, and copper alloy have the characteristics of low electricalresistance and high thermal conductivity, so that an extremely largeamount of energy is required in order to weld them.

The following methods have long been known as methods for weldingtogether the electrode plate substrates and collector members thatconstitute the generation element:

1) Laser welding

2) Ultrasonic welding

3) Resistance welding

As regards the laser welding method, aluminum, aluminum alloy, copper,and copper alloy, which are the materials to be welded, have a highreflectivity of around 90% with respect to the YAG(yttrium-aluminum-garnet) laser beams that are widely used for metalwelding, and therefore will require a high-energy laser beam.Additionally, with laser welding of aluminum, aluminum alloy, copper, orcopper alloy, there exist the problems that the weldability variesgreatly depending on influences of surface conditions, and that, as withlaser welding of other materials, the occurrence of spatter isunavoidable.

With ultrasonic welding, a large energy is required because of the highthermal conductivity of aluminum, aluminum alloy, copper, and copperalloy, which are the materials to be welded, and there is also the issuethat the positive electrode active material and negative electrodeactive material are prone to fall out due to ultrasonic vibration duringthe welding.

With resistance welding, furthermore, there are the issues that a largecurrent has to be input in a short time because of the low electricalresistance and high thermal conductivity of aluminum, aluminum alloy,copper, and copper alloy, which are the materials to be welded; thatthere is risk of the resistance welding electrode rods becomingfusion-welded to the collector members during the resistance welding,and that melting or sparks can occur in places other than the weldportions.

The three welding methods each have their merits and drawbacks asdescribed above. However, in the interest of productivity and economy,it is preferable to employ resistance welding, which has long beenwidely used as a method for welding between metals. However, theelectrode assemblies in the lithium ion secondary batteries or otherprismatic sealed secondary batteries used in EVs and HEVs have astructure in which positive electrode plates and negative electrodeplates are stacked or wound with separators interposed therebetween.Furthermore, the substrate exposed portions of the positive electrodeplates and negative electrode plates are disposed so as to be located ondiffering sides to each other, with the stacked positive electrode platesubstrate exposed portions being welded to the positive electrodecollector member, and likewise with the stacked negative electrode platesubstrate exposed portions being welded to the negative electrodecollector member. Where the capacity of a lithium ion secondary batteryor other prismatic sealed secondary battery used for an EV or HEV islarge, the number of these stacked positive electrode plate substrateexposed portions and negative electrode plate substrate exposed portionswill be extremely large.

JP-A-2003-249423 discloses the invention of a storage element having anelectrode assembly formed of positive electrode plates and negativeelectrode plates wound into a flattened shape with separators interposedtherebetween, in which the substrate exposed portions of each electrodeare divided into two bundles for welding to the collector member, inorder to render small the stacking width of the respective electrodesubstrate exposed portions that project out from the separators. Thestructure of the storage element disclosed in JP-A-2003-249423 will nowbe described using FIGS. 9 and 10. FIG. 9A is a cross-sectional view ofan electrical double layer capacitor that serves as the storage elementdisclosed in JP-A-2003-249423, FIG. 9B is a cross-sectional view alongline IXB-IXB in FIG. 9A, FIG. 9C is a cross-sectional view along lineIXC-IXC in FIG. 9A, and FIG. 10 is a view showing the welding processbetween the electrode substrate exposed portions and collector member inFIGS. 9A to 9C.

As FIGS. 9A to 9C show, the storage element 50 has a wound electrodeassembly 51 in which positive electrode plates, negative electrodeplates and interposed separators (all of which are not shown in thefigures) are stacked and wound in a flattened shape, and this woundelectrode assembly 51 is disposed inside a prismatic outer can 52 madeof aluminum. The positive electrode collector member 53 a and negativeelectrode collector member 53 b of the storage element 50 have aU-shaped wing portion 54 a or 54 b, respectively, formed at one end andconnected to the substrate exposed portions 55 a of the positiveelectrode plates or the substrate exposed portions 55 b of the negativeelectrode plates, respectively, with the other end being connected tothe positive electrode terminal 56 a or negative electrode terminal 56b, respectively. Furthermore, the substrate exposed portions 55 a of thepositive electrode plates are divided into two bundles, of which one iswelded to one outer side face of the U-shaped wing portion 54 a and theother to the other outer side face, and likewise, the substrate exposedportions 55 b of the negative electrode plates are divided into twobundles, one of which is welded to one outer side face of the otherU-shaped wing portion 54 b and the other to the other outer side face.

For the positive electrode, for example, ultrasonic welding is performedas follows, as shown in FIG. 10. One of the two split bundles ofsubstrate exposed portions 55 a of the positive electrode plates isdisposed on an outer face of the U-shaped wing portion 54 a, a horn 57of an ultrasonic welding device (not shown in the figure) is broughtinto contact with the outer surface of the substrate exposed portions 55a, and an anvil 58 is disposed on the inner surface of the U-shaped wingportion 54 a. Note that the other bundle of the substrate exposedportions 55 a of the positive electrode plates is ultrasonically weldedwith the same method, and likewise with the negative electrode.

In the case where the two split bundles of positive electrode plates ornegative electrode plates are resistance welded, one will considereither the method of welding each bundle separately or the method ofseries spot welding the bundles simultaneously. Of these, the seriesspot welding method will be preferable in view of the smaller number ofweldings. With the long-used series spot welding technique, in the casewhere, as shown in FIG. 11, members to be welded 73 and 74 are welded attwo spots coaxially with a pair of resistance welding electrode rods 71and 72, the method that has mainly been used is to interpose a U-shapedwelding piece 75 in the intermediate space and perform the weldings atthe top and bottom of the U-shaped welding piece 75. This method is inwide general use because the U-shaped welding piece 75 can be fabricatedwith ease from flat sheet metal and because it is easy to fabricateprojections that will render the resistance welding both easy andstable.

The invention disclosed in JP-A-2003-249423 yields the advantage that awidth of the positive electrode exposed portions and of the negativeelectrode exposed portions can be rendered small, and thereforevolumetric efficiency of the storage device will be good. However, withthis invention, there exist problematic aspects that will render themanufacturing equipment complex. These include the fact that severalweldings are required in order to weld the positive electrode plates andthe negative electrode plates to the positive electrode collector memberand negative electrode collector member, respectively; and furthermore,that an open space is needed in the central portion of the woundelectrode assembly in order for disposition of the welding-purposeU-shaped wing portions of the positive electrode collector member andnegative electrode collector member, and that it is necessary to disposean anvil in the interior of the U-shaped wing portions during theultrasonic welding.

In addition, although it is stated in JP-A-2003-249423 that theultrasonic welding method will preferably be used for the process ofwelding the electrode plates, a number of winding turns in theembodiments is 16 (8 for each of the two split bundles), and a stackthickness is 320 μm. As opposed to this, in large-capacity sealedbatteries such as the lithium ion secondary batteries for EVs and HEVs,the number of stacked positive electrode substrate exposed portions andnegative electrode substrate exposed portions is much greater than inthe case of the invention disclosed in JP-A-2003-249423, and moreoverthe stack thickness is far larger.

Therefore, with large-capacity prismatic sealed batteries such as thelithium ion secondary batteries for EVs and HEVs, in order to use theultrasonic welding method to weld in a stable condition the stackedpositive electrode substrate exposed portions and negative electrodesubstrate exposed portions to the collector members, a large applicationof pressure is required to fit the stacked positive electrode substrateexposed portions and negative electrode substrate exposed portionstightly against their respective collector members, and a large energyis required to make the ultrasonic vibration reach as far as the otherends of the stacked positive electrode substrate exposed portions andnegative electrode substrate exposed portions. With the inventiondisclosed in JP-A-2003-249423, the pressure application and ultrasonicenergy have to be sustained by the anvil disposed in the interior of theU-shaped collector members, which means that the anvil must haveconsiderable rigidity, and in addition it is extremely difficult intechnical terms to find stable welding conditions under which an anvilof the size that can be provided in the collector member interior willsustain the large pressure application.

Furthermore, with the long-used method shown in FIG. 11, the positiveelectrode substrate exposed portions and negative electrode substrateexposed portions can each be series-welded with a single welding, butmeasures such as providing a pressure receiving piece 76 in the interiorof the U-shaped welding piece 75 and/or a metal block for powerconduction are needed in order to eliminate distortion of the U-shapedwelding piece 75 due to pressure application by the welding electroderods 71 and 72, and such complexification of the welding equipment hasbeen an issue.

In JP-UM-A-58-113268 there is disclosed an electrode plate substrateyoke 80, shown in FIG. 12, in which electrode substrate groups 84 a and84 b, formed by splitting into two bundled groups the substrates 84 ofan electrode assembly 83, are placed against the side faces of the baseportion 82 of a collector member 81 and integrally series spot-weldedthereto together with a pair of stiffening plates 85 a and 85 b disposedon the outer sides of the electrode substrate groups 84 a and 84 b.

JP-A-2000-40501 discloses a flat wound electrode battery 90 that, asshown in FIGS. 13A and 13B, has a flattened wound electrode assembly 93with positive electrode plates and negative electrode plates wound insuch a manner, with separators interposed therebetween, that positiveelectrode substrate exposed portions 91 and negative electrode substrateexposed portions 92 are disposed on opposing sides; and in which, usingfor example a positive electrode terminal 94 consisting of a rectangularconnecting part 94 a that has edge portions made into curved surfacesand that fits into the central hollow space 91 a around which thepositive electrode substrate exposed portions 91 are wound, a terminalpart 94 b that projects longitudinally in the flattening direction,orthogonal to the winding axis direction, and a short connecting part 94c that connects such two parts, electrical connection is effected byfitting the terminal part 94 b of the positive electrode terminal 94into the central hollow space 91 a around which the positive electrodesubstrate exposed portions 91 are wound (see FIG. 13A), then performingseries spot welding on both sides of the positive electrode substrateexposed portions 91.

However, with the series spot welding methods disclosed inJP-UM-A-58-113268 and JP-A-2000-40501, the substrate exposed portions ofthe positive electrode plates and negative electrode plates are splitinto two groups and series spot welded directly to the two sides of thepositive electrode terminal or negative electrode terminal,respectively, and because such welding surfaces on the positiveelectrode terminal or negative electrode terminal are flat surfaces, ithas been difficult to render high the strength of the weldings betweenthe positive electrode terminal or negative electrode terminal and thesubstrate exposed portions of the positive electrode plates or negativeelectrode plates, respectively, and to render small the variation in theinternal resistance of the welds. In addition, there has been the issuethat the positive electrode terminal and negative electrode terminalmust be substantial bodies, which means that the mass of the positiveelectrode terminal and negative electrode terminal will be large.

In large-capacity prismatic sealed secondary batteries such as thelithium ion secondary batteries for EVs and HEVs, the number of stackedpositive electrode substrate exposed portions and negative electrodesubstrate exposed portions is extremely large, and moreover aluminum oraluminum alloy is used for the positive electrode substrates andpositive electrode collector, and copper or copper alloy for thenegative electrode substrates and negative electrode collector. Sincealuminum, aluminum alloy, copper and copper alloy are materials with lowelectrical resistance and with good thermal conductivity, it isdifficult to render high the strength of the welding between thepositive electrode substrate exposed portions and positive electrodeterminal and between the negative electrode substrate exposed portionsand negative electrode terminal, and still more difficult to rendersmall variation in the internal resistance of the welds.

SUMMARY

An advantage of some aspects of the present invention is to provide aprismatic sealed secondary battery in which the stacked substrateexposed portions of the positive electrode or of the negative electrode,or of both, are split into two groups, a connecting conductive member isstably positioned and disposed therebetween, resistance welding isperformed between the substrate exposed portions and the collectormembers and between the substrate exposed portions and the connectingconductive members, so that enhanced resistance of the welds can berealized, and moreover variation in the welding strength is curbed.

According to an aspect of the invention, a prismatic sealed secondarybattery includes: an electrode assembly that has stacked or woundpositive electrode substrate exposed portions and negative electrodesubstrate exposed portions; a collector member that is electricallyjoined to the positive electrode substrate exposed portions; a collectormember that is electrically joined to the negative electrode substrateexposed portions; and a prismatic outer can into which the electrodeassembly is inserted in such a manner that the positive electrodesubstrate exposed portions are positioned at one end, and the negativeelectrode substrate exposed portions at the other end, of the prismaticouter can. The positive electrode substrate exposed portions or thenegative electrode substrate exposed portions, or both, are split intotwo groups, and therebetween is disposed an intermediate member that ismade of a resin material and holds one or more connecting conductivemembers. The collector member for the substrate exposed portions thatare split into two groups is disposed on at least one of the outermostfaces of the substrate exposed portions that are split into two groups,and is electrically joined by a resistance welding method to thesubstrate exposed portions that are split into two groups, together withthe one or more connecting conductive members of the intermediatemember. The resin material portion of the intermediate member protrudes,in the extension direction of the substrate exposed portions that aresplit into two groups, beyond the ends of the substrate exposed portionsthat are split into two groups and the ends of the collector member tothe prismatic outer can.

With such a prismatic sealed secondary battery of the present aspect,the intermediate member that is made of resin material and holds atleast one connective conducting member is disposed between the two splitgroups of positive electrode substrate exposed portions, or of negativeelectrode substrate exposed portions, or of both. The collector memberfor the substrate exposed portions that are split into two groups isdisposed on at least one of the outermost faces of the substrate exposedportions that are split into two groups and is electrically joined by aresistance welding method to the substrate exposed portions that aresplit into two groups, together with the one or more connectingconductive members of the intermediate member.

Consequently, with the prismatic sealed secondary battery of the presentaspect, the substrate exposed portions that are split into two groupscan be joined to the connecting conductive members and the collectormember in a single operation using the series resistance welding method.In addition, when connecting conductive members are provided inplurality, because the plurality of connecting conductive members areheld by the intermediate member made of resin material, the precision ofthe dimensions among the plurality of connecting conductive members canbe improved, and moreover they can be positioned and disposed betweenthe two split groups of substrate exposed portions in a stable state, sothat the quality of the resistance welds is improved, enabling loweredresistance to be realized. For these reasons, a prismatic sealedsecondary battery with raised output and lessened output variation isobtained with the present aspect of the invention.

With such a prismatic sealed secondary battery of the present aspect,the resin material portions of the intermediate member protrude, in theextension direction of the two split groups of substrate exposedportions, beyond the ends of the two split substrate exposed portionsand the ends of the collector member to the prismatic outer can. Sincethe electrode assembly is inserted into the prismatic outer can in sucha manner that the positive electrode substrate exposed portions arepositioned at one end, and the negative electrode substrate exposedportions at the other end, of the prismatic outer can, in such aprismatic sealed secondary battery of the present aspect, the protrudingresin material portions of the intermediate member will be positioned atthe two inside ends of the prismatic outer can, thus eliminating therisk of the ends of the two split groups of substrate exposed portionsand the ends of the collector member contacting with the two inside endsof the prismatic outer can. Hence, such a prismatic sealed secondarybattery of the present aspect will be a highly reliable prismatic sealedsecondary battery in which the risk of the positive electrode substrateexposed portions and/or the negative electrode substrate exposedportions short-circuiting with the prismatic outer can is suppressed.

Note that usually in prismatic sealed secondary batteries, the electrodeassembly is wrapped in a folded-back plate-like resin sheet wheninserted into the prismatic outer can, and with the prismatic sealedsecondary battery of the present aspect, even if the resin sheet ismispositioned, contacting of the positive electrode substrate exposedportions and/or the negative electrode substrate exposed portions withthe prismatic outer can will be reliably suppressed because theprotruding resin material portions of the intermediate member will bepositioned at the two inside ends of the prismatic outer can of theelectrode assembly. In addition, if external force should act on theprismatic sealed secondary battery of the present aspect and deform theouter can, the possibility of the positive electrode substrate exposedportions and/or the negative electrode substrate exposed portionscontacting with the prismatic outer can will be smaller than in the casewhere the electrode assembly is covered simply by a resin sheet, becausethe resin material portions of the intermediate member are rigid bodiesand therefore are not likely to deform. Thus, a prismatic sealedsecondary battery with high reliability can be obtained.

In addition, the resin material portion of the intermediate member is ofsuch a size as to protrude beyond both the ends of the substrate exposedportions and the ends of the collector member when the intermediatemember has been inserted between the two split groups of positiveelectrode substrate exposed portions and/or of negative electrodesubstrate exposed portions, which means that the intermediate member canbe clasped at its protruding resin material portion when it is insertedbetween the two split groups of substrate exposed portions, therebyyielding additional advantages of facilitating insertion, facilitatingthe clasping of the intermediate member, and facilitating assembly.

Note that with the prismatic sealed secondary battery of the presentaspect, the intermediate member, which is made of resin material, willbe provided with one or more connecting conductive members, but sincewith one connecting conductive member the intermediate member made ofresin material is prone to move rotationally with the weld point of theconnecting conductive member as pivot point, the intermediate membermade of resin material is preferably provided with a plurality ofconnecting conductive members in order to stabilize disposition of theintermediate member made of resin material and enable large-currentcharge/discharge. Additionally, in the prismatic sealed secondarybattery of the present aspect, an intermediate member made of resinmaterial may be disposed on the positive electrode substrate exposedportions or on the negative electrode substrate exposed portions, or onboth, but will preferably be provided on both.

Note that in the present aspect of the invention, although a collectormember for the two split groups of substrate exposed portions may bedisposed on either or both of the outermost faces of the two splitgroups of substrate exposed portions, it is preferable that a collectormember be disposed on both such outermost faces. However, by disposingon the other of the two outermost faces of the two split groups ofsubstrate exposed portions a collection receiving member that is notdirectly connected to the electrode terminal, a functional effect can beexerted that is substantially the same as the case where a collectormember is disposed on both outermost faces of the two split groups ofsubstrate exposed portions. Hence, the meaning of “collector member” asused herein includes such a “collection receiving member”.

Note further that resistance welding can be executed in a morephysically stable state if a collector member is disposed on both of theoutermost faces of the two split groups of substrate exposed portions.Moreover, it will be possible not to dispose anything on the other ofthe two outermost faces of the two split groups of substrate exposedportions, and to perform the resistance welding by bringing one of thepairs of resistance welding electrodes directly into contact with thatface. However, in that case, there will be a possibility of fusionoccurring between the resistance welding electrodes and the other of thetwo outermost faces of the two split groups of substrate exposedportions. Therefore, it will be preferable either to dispose on each ofthe two outermost faces of the two split groups of substrate exposedportions a collector member that is connected to the electrode terminal,or else to dispose on one of such faces a collector member connected tothe electrode terminal and dispose on the other of such faces acollection receiving member that serves as a collector member.

Examples of the resin material that can be used for the intermediatemember in the prismatic sealed secondary battery of the present aspectinclude polypropylene (PP), polyethylene (PE), polyvinylidene chloride(PVDC), polyacetal (POM), polyamide (PA), polycarbonate (PC), andpolyphenylene sulfide (PPS).

In the prismatic sealed secondary battery of the present aspect, it ispreferable that flat portions be provided on portions of the resinmaterial portion of the intermediate member that are opposed to theprismatic outer can. In such a case, it is preferable that chamferedportions be formed on the angled portions of the resin material portionof the intermediate member that are opposed to the prismatic outer can.

With flat portions being provided on those portions of the resinmaterial portion of the intermediate member that are opposed to theprismatic outer can, assembly will be easier, because by placing theflat portions of the resin material portion of the intermediate memberagainst at least one of the two ends of the prismatic outer can duringinsertion of the electrode assembly into the prismatic outer can, theelectrode assembly can be inserted by being slid in. Moreover, withchamfered portions being formed on the angled portions of the resinmaterial portion of the intermediate member that are opposed to theprismatic outer can, insertion into the prismatic outer can will beeasier, and furthermore, even where the electrode assembly is wrapped ina folded-back plate-like resin sheet when inserted into the prismaticouter can, ripping of the resin sheet by the angled portions of theresin material portion of the intermediate member will be suppressed.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that chamfered portions be formed on the angled portions ofthe resin material portion of the intermediate member that are on theside that is inserted into the substrate exposed portions that are splitinto two groups.

With chamfered portions being formed on the angled portions of the resinmaterial portion of the intermediate member that are on the side that isinserted into the two split groups of substrate exposed portions in theprismatic sealed secondary battery of the present aspect, duringinsertion of the intermediate member between the stacked substrateexposed portions, the intermediate member, having the chamfered portionsformed in it, will seldom cause damage to the pliable substrate exposedportions if it contacts them, and the connecting conductive members caneasily be made to contact against the substrate exposed portions. As aresult, the weldability will be improved.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the intermediate member be provided with a gas ventinghole or cutout, or both.

If the intermediate member is provided with gas venting holes orcutouts, any gas that may be generated in the electrode assemblyinterior in the event that abnormality occurs in the battery can easilybe expelled to the exterior of the electrode assembly, and since thepressure-reduction type current interruption mechanism, gas exhaustvalve, and so forth, with which a prismatic sealed battery is normallyequipped will be activated stably, safety can be secured. In addition,the volume of the intermediate member will be reduced, and therefore itwill be possible to render the prismatic sealed battery lighter.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the connecting conductive member(s) be block-shaped orcolumnar body-shaped.

With the connecting conductive members being block-shaped or columnarbody-shaped in the prismatic sealed secondary battery of the presentaspect, deformation will be unlikely to occur when the pushing pressureis applied during resistance welding, the physical properties of thewelds will be stabilized, and moreover the quality of the welds will begood. Note that shapes that are not liable to deformation, such ascylindrical columnar, square columnar, elliptical columnar, circularcylindrical, square cylindrical, or elliptical cylindrical, can beemployed for the shape of the connecting conductive members.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the angled portions of two mutually opposed surfaces ofthe block shapes or columnar body shapes have chamfered portions.

With the angled portions of two mutually opposed surfaces of the blockshapes or columnar body shapes having chamfered portions in theprismatic sealed secondary battery of the present aspect, duringinsertion of the intermediate member between the stacked substrateexposed portions, the connecting conductive members will cause littledamage to the pliable substrate exposed portions if they contact them,and the connecting conductive members can easily be made to contactagainst the substrate exposed portions. As a result, the weldabilitywill be improved. Moreover, since the areas of the two opposed surfacesof the connecting conductive members become small, those surfaces willact as projections, which means that current will be concentrated andheat-up will readily take place, so that the physical properties of thewelds will be stabilized, and moreover the quality of the welds will begood.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the surfaces provided with the chamfered portions of theconnecting conductive member(s) be planes.

The surfaces provided with the chamfered portions of the connectingconductive members can take the form either of curved surfaces or ofplanes. However, if the surfaces provided with the chamfered surfacestake the form of planes, then during insertion of the intermediatemember between the stacked substrate exposed portions, the surfaces withchamfered angled portions and the surfaces of the intermediate memberwhere the connecting conductive members are exposed will, of necessity,form obtuse angles with respect to the substrate exposed portions. Forthis reason, the substrate exposed portions and the connectingconductive members will readily come into contact when the intermediatemember is inserted between the stacked substrate exposed portions andresistance welding is performed in the prismatic sealed secondarybattery of the present aspect. As a result, the weldability will beimproved.

The invention will be described with reference to the accompanyingdrawings, wherein the same numbers refer to the same elementsthroughout.

FIG. 1A is a cross-sectional view of a nonaqueous electrolyte secondarybattery of the First Embodiment, FIG. 1B is a cross-sectional view alongline IB-IB in FIG. 1A, FIG. 1C is a cross-sectional view along lineIC-IC in FIG. 1A, and FIG. 1D is an enlarged view of the portion ID inFIG. 1C.

FIG. 2A is a top view of a positive electrode connecting conductivemember in a First Embodiment of the invention, FIG. 2B is across-sectional view along line IIB-IIB in FIG. 2A, FIG. 2C is a frontview of the positive electrode connecting conductive member, FIG. 2D isa front view of a positive electrode intermediate member, FIG. 2E is aside view of FIG. 2D, FIG. 2F is a top view of a modification in which achamfered position in the positive electrode intermediate member ismodified, and FIG. 2G is a top view showing a state in which thepositive electrode intermediate member in FIG. 2F is mounted on anelectrode assembly.

FIG. 3 is a side view showing the welding conditions pertaining to theFirst Embodiment.

FIG. 4A is a view showing the route by which the resistance weldingcurrent flows in the case where the portion of the protrusion thatcontacts with the positive electrode substrate exposed portions isannular, FIG. 4B is a view showing the portions in FIG. 4A where heat-upis intense, FIG. 4C is a view showing the route by which the resistancewelding current flows in the case where the portion of the protrusionthat contacts with the positive electrode substrate exposed portions iscircular, and FIG. 4D is a view showing the portions in FIG. 4C whereheat-up is intense.

FIGS. 5A to 5C are schematic views showing the shape of the positiveelectrode connecting conductive member pertaining to Second to FourthEmbodiments, respectively, of the invention, and FIG. 5D is a schematicside view showing the positive electrode intermediate member of theFourth Embodiment in the state where it has been installed to thepositive electrode substrate exposed portions, which are split into twogroups.

FIG. 6A is a side view showing the post-welding disposition of thepositive electrode connecting conductive member portion in a FifthEmbodiment of the invention, and FIG. 6B is a side view showing thepost-welding disposition of the positive electrode connecting conductivemember portion in a Sixth Embodiment of the invention.

FIGS. 7A to 7C are front views showing the shape of the positiveelectrode intermediate member in Seventh to Ninth Embodiments,respectively, of the invention.

FIG. 8A is a front view of the positive electrode connecting conductivemember in a Tenth Embodiment of the invention, FIG. 8B is a longitudinalsectional view through FIG. 8A, FIG. 8C is a top view of the ring-shapedinsulating seal material, and FIG. 8D is a longitudinal sectional viewof the positive electrode intermediate member in the Tenth Embodiment.

FIG. 9A is a cross-sectional view of an electrical double layercapacitor which serves as a storage element in the related art, FIG. 9Bis a cross-sectional view along line IXB-IXB in FIG. 9A, FIG. 9C is across-sectional view along line IXC-IXC in FIG. 9A.

FIG. 10 is a view showing the welding process between the electrodesubstrate exposed portion and collector member in FIGS. 9A to 9C.

FIG. 11 is a view explicating the series spot welding method that haslong been in use.

FIG. 12 is a cross-sectional view of an electrode plate substrate yokethat has been welded with the series spot welding method that has longbeen in use.

FIG. 13A is an exploded perspective view of a positive electrodeterminal and positive electrode substrate exposed portions in thepre-welding state in another example of the related art, and FIG. 13B isa perspective view of those items in the post-welding state.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments for carrying out the invention will now bedescribed in detail with reference to the accompanying drawings.However, it should be remembered that the various embodiments set forthbelow are intended by way of examples for understanding the technicalconcepts of the invention, and not by way of limiting the invention tothese particular prismatic sealed secondary batteries. The invention canequally well be applied to produce many different variants of theembodiments without departing from the scope and spirit of the technicalconcepts set forth in the claims. Note that although the invention isapplicable to a flattened battery that uses a generation element, aplurality of positive electrode substrate exposed portions formed at oneend and a plurality of negative electrode substrate exposed portionsformed at the other end, which can be made either by stacking or bywinding positive electrode plates and negative electrode plates withseparators interposed therebetween, the embodiment descriptions belowuse flattened wound electrode assemblies as representative examples.

First Embodiment

First of all, as an example of a prismatic sealed secondary battery of aFirst Embodiment of the invention, a prismatic nonaqueous electrolytesecondary battery will be described using FIGS. 1 to 3. FIG. 1A is across-sectional view of a nonaqueous electrolyte secondary battery ofthe First Embodiment, FIG. 1B is a cross-sectional view along line IB-IBin FIG. 1A, FIG. 1C is a cross-sectional view along line IC-IC in FIG.1A, and FIG. 1D is an enlarged view of the portion ID in FIG. 1C. FIG.2A is a top view of a positive electrode connecting conductive member inthe First Embodiment, FIG. 2B is a cross-sectional view along lineIIB-IIB in FIG. 2A, FIG. 2C is a front view of the positive electrodeconnecting conductive member, FIG. 2D is a front view of a positiveelectrode intermediate member, FIG. 2E is a side view of FIG. 2D, FIG.2F is a top view of a modification in which a chamfered position in thepositive electrode intermediate member is modified, and FIG. 2G is a topview showing a state in which the positive electrode intermediate memberin FIG. 2F is mounted on an electrode assembly. FIG. 3 is a side viewshowing the welding conditions pertaining to the First Embodiment.

This nonaqueous electrolyte secondary battery 10 has a flattened woundelectrode assembly 11 in which positive electrode plates and negativeelectrode plates are wound with separators interposed therebetween (allof these are not shown in the figures). The positive electrode platesare fabricated by spreading positive electrode active material mixtureover both faces of a positive electrode substrate constituted ofaluminum foil, drying such mixture and rolling the resulting plate, thenslitting the plate so that a strip of aluminum foil is exposed.Likewise, the negative electrode plates are fabricated by spreadingnegative electrode active material mixture over both faces of a negativeelectrode substrate constituted of copper foil, drying such mixture androlling the resulting plate, then slitting the plate so that a strip ofcopper foil is exposed.

Next, the positive electrode plates and negative electrode plates thusobtained are displaced so that the aluminum foil exposed portions of thepositive electrode plates do not overlie the active material layer ofone of the opposed electrodes, and the copper foil exposed portions ofthe negative electrode plates do not overlie the active material layerof the other opposed electrode, and are then wound with polyethyleneporous separators interposed therebetween, to produce a flattened woundelectrode assembly 11 that has a plurality of positive electrodesubstrate exposed portions 14 piled one above another at one end in thewinding axis direction, and a plurality of negative electrode substrateexposed portions 15 piled one above the other at the other end.

The plurality of positive electrode substrate exposed portions 14 arestacked and connected via positive electrode collector members 16 to apositive electrode terminal 17, and likewise the plurality of negativeelectrode substrate exposed portions 15 are stacked and connected vianegative electrode collector members 18 to a negative electrode terminal19. Note that the positive electrode terminal 17 and the negativeelectrode terminal 19 are each fixed to a sealing plate 13 with aninsulating member 20, 21 respectively, interposed. To fabricate thisprismatic nonaqueous electrolyte secondary battery 10 of the FirstEmbodiment, the flattened wound electrode assembly 11 fabricated in theforegoing manner is inserted, with an insulating resin sheet 23interposed all around except for the sealing plate 13 edge, into aprismatic outer can 12, after which the sealing plate 13 is laser-weldedto the mouth portion of the outer can 12, then nonaqueous electrolyte ispoured in through an electrolyte pour hole 22, and the electrolyte pourhole 22 is sealed over.

In the positive electrode part of the flattened wound electrode assembly11, as shown in FIGS. 1B and 1C, the stacked plurality of positiveelectrode substrate exposed portions 14 are split into two groups,between which is sandwiched a positive electrode intermediate member 24that is constituted of resin material and holds one or more (two in thisexample) positive electrode connecting conductive members 24A. Likewisein the negative electrode part, the stacked plurality of negativeelectrode substrate exposed portions 15 are split into two groups,between which is sandwiched a negative electrode intermediate member 25that is constituted of resin material and holds two negative electrodeconnecting conductive members 25A. Also, on each of the two outermostsurfaces of the positive electrode substrate exposed portions 14,located at the two sides of the positive electrode connecting conductivemembers 24A, there is disposed a positive electrode collector member 16,and on each of the two outermost surfaces of the negative electrodesubstrate exposed portions 15, located at the two sides of the negativeelectrode connecting conductive members 25A, there is disposed anegative electrode collector member 18. Specific structures and featuresof the positive electrode intermediate member 24, the negative electrodeintermediate member 25, the positive electrode connecting conductivemembers 24A, and the negative electrode connecting conductive members25A will be described in greater detail later.

Note that the positive electrode connecting conductive members 24A aremade of the same material, namely, aluminum, as the positive electrodesubstrates, and the negative electrode connecting conductive members 25Aare made of the same material, namely, copper, as the negative electrodesubstrates, but the shapes of the positive electrode connectingconductive members 24A and the negative electrode connecting conductivemembers 25A may either be the same or differ. Examples of the resinmaterial that can be used for the positive electrode intermediate member24 and the negative electrode intermediate member 25 are syntheticresins such as polypropylene (PP), polyethylene (PE), polyvinylidenechloride (PVDC), polyacetal (POM), polyamide (PA), polycarbonate (PC),and polyphenylene sulfide (PPS).

Note that in the nonaqueous electrolyte secondary battery 10 of theFirst Embodiment, as FIGS. 1A, 1B and 2D show, the positive electrodeintermediate member 24 and the negative electrode intermediate member 25hold two positive electrode connecting conductive members 24A ornegative electrode connecting conductive members 25A, respectively, asan example, but the number of positive electrode connecting conductivemembers 24A or negative electrode connecting conductive members 25A thatis provided may alternatively, depending on the battery output, forexample, that is required, be one, or be three or more. In particular,when a plurality of connecting conductive members are provided in anintermediate member, the fact that all of the connecting conductivemembers are held by one intermediate member that is made of resinmaterial will mean that the precision of the dimensions among theconnecting conductive members can be improved, and moreover that theycan be positioned and disposed between the two split groups of substrateexposed portions in a stable state.

Resistance welding is performed both between these positive electrodecollector members 16 and the positive electrode substrate exposedportions 14, and between the positive electrode substrate exposedportions 14 and the positive electrode connecting conductive members 24A(at four places in each case, see FIG. 1B). Likewise, connection iseffected, by resistance welding, between the negative electrodecollector members 18 and the negative electrode substrate exposedportions 15, and between the negative electrode substrate exposedportions 15 and the negative electrode connecting conductive members 25A(at four places in each case).

Detailed descriptions will now be given, using FIGS. 2 and 3, of thespecific manufacturing method for the flattened wound electrode assembly11, together with the resistance welding method using the positiveelectrode substrate exposed portions 14, the positive electrodecollector members 16 and the positive electrode intermediate member 24having positive electrode connecting conductive members 24A, and of theresistance welding method using the negative electrode substrate exposedportions 15, the negative electrode collector members 18 and thenegative electrode intermediate member 25 having negative electrodeconnecting conductive members 25A. Since, however, the shapes of thepositive electrode connecting conductive members 24A and positiveelectrode intermediate member 24 can be substantially identical withthose of the negative electrode connecting conductive members 25A andnegative electrode intermediate member 25, and moreover since theresistance welding methods in both cases are substantially similar, thedescriptions below use the positive electrode plate items asrepresentative examples.

First of all, the positive electrode substrate exposed portions 14 ofthe flattened wound electrode assembly 11, which had been obtained bydisplacing the positive electrode plates and negative electrode platesso that the aluminum foil exposed portions of the positive electrodeplates did not overlie the active material layer of one of the opposedelectrodes, and the copper foil exposed portions of the negativeelectrode plates did not overlie the active material layer of the otheropposed electrode, then winding the electrode plates with polyethyleneporous separators interposed therebetween, were split into two groups,one on either side from the central portion of the winding, and eachgroup of positive electrode substrate exposed portions 14 was bundledcentered on ¼ of the electrode assembly thickness. The thickness of thealuminum foil bundle in each group is approximately 660 μm, and thetotal number of stacked foils is 88 (44 in each group). The positiveelectrode collector members 16 are fabricated by punching andbend-processing, etc., an 0.8-mm thick aluminum sheet. Note that thepositive electrode collector members 16 may alternatively be fabricatedby casting, etc., from aluminum sheet.

Then the positive electrode collector members 16 and the positiveelectrode intermediate member 24 having positive electrode connectingconductive members 24A are inserted between the two split groups ofpositive electrode substrate exposed portions 14, with the positiveelectrode collector members 16 being inserted onto the two outermostsurfaces of the positive electrode substrate exposed portions 14 and thepositive electrode intermediate member 24 being inserted into the innerperiphery thereof, in such a manner that truncated cone shapedprotrusions 24 b of the positive electrode intermediate member 24 eachcontact against the positive electrode substrate exposed portions 14.

There follows an explication, using FIGS. 2A to 2G, of the shape of thepositive electrode connecting conductive members 24A held by thepositive electrode intermediate member 24 in the First Embodiment. Inthese positive electrode connecting conductive members 24A, a protrusion24 b with, e.g., a truncated cone shape is formed on each of two opposedfaces 24 e of the cylindrical columnar main body 24 a. In the centralportion of this truncated cone-shaped protrusion 24 b there is formed anaperture 24 c extending from the tip into the interior of thecylindrical columnar main body 24 a. Angled portions 24 f are formedbetween the two opposed faces 24 e and the side surfaces of thecylindrical columnar main body 24 a.

It is desirable that the height H of the truncated cone-shapedprotrusion 24 b be comparable with that of protrusions (projections)that are ordinarily formed on resistance welding members, that is,several mm or so. As regards the depth D of the aperture 24 c, which inthe present example is larger than the height of the truncatedcone-shaped protrusion 24 b, the aperture 24 c will preferably be formedfrom a face 24 e, where the protrusion 24 b is formed, of thecylindrical columnar main body 24 a, as far as a position located inwardto a distance less than the height H of the protrusion 24 b (with thedepth D of the aperture 24 c being less than 2H), or more preferably, asfar as a position located inward to a distance less than ½ of the heightH of the protrusion 24 b from the surface of the cylindrical columnarmain body 24 a where the protrusion 24 b is provided (with the depth Dof the aperture 24 c being less than 3/2 H).

It is desirable that the diameter and length of the cylindrical columnarmain body 24 a be on the order of three mm to several tens of mm, thoughthese dimensions will vary with the flattened wound electrode assembly11, outer can 12, and other parts (see FIGS. 1A to 1D). Note thatalthough the shape of the main body 24 a of the positive electrodeconnecting conductive members 24A is described here as cylindricalcolumnar, any desired shape that has the form of a metallic block, suchas square columnar or elliptical columnar can be used. Also, as thematerial for forming the positive electrode connecting conductivemembers 24A, copper, copper alloy, aluminum, aluminum alloy, tungsten,molybdenum, or the like, can be used. Furthermore, variants of suchitems constituted of such metals can be used, by for example applyingnickel plating to the protrusion 24 b, or changing the material of theprotrusion 24 b and its base area to tungsten or molybdenum, whichpromotes heat emissions, and joining it by brazing, for example, to themain body 24 a of the positive electrode connecting conductive members24A constituted of copper, copper alloy, aluminum, or aluminum alloy.

Note that in the First Embodiment, there are two positive electrodeconnecting conductive members 24A, which are held integrally by thepositive electrode intermediate member 24 that is made of resinmaterial. In such a case, the plurality of positive electrode connectingconductive members 24A are held in such a manner as all to be parallelto each other. The shape of the positive electrode intermediate member24 can take any square columnar, elliptical columnar, or like form, thatis desired, but is configured to have a horizontally long squarecolumnar form in order to be stably positioned and fixed in the positiveelectrode substrate exposed portions 14 split into two groups.

The length w of the square columnar positive electrode intermediatemember 24 will vary with the size of the prismatic nonaqueouselectrolyte secondary battery, but can be on the order of 20 mm toseveral tens of mm. As for the width h, although it is desirable thatthis be roughly the same as the height of the positive electrodeconnecting conductive members 24A, but it will suffice if at least thetwo ends of the positive electrode connecting conductive members 24Athat will become welds are exposed. Note that the two ends of thepositive electrode connecting conductive members 24A will preferablyprotrude from the surface of the positive electrode intermediate member24, but that they do not necessarily need to do so.

As FIG. 1D shows, in the resin material portion 24 p of the positiveelectrode intermediate member 24, there is formed, in the extensiondirection of the two split groups of positive electrode substrateexposed portions 14, a protruding portion 24 t that protrudes beyond theends 14 t of the two split groups of positive electrode substrateexposed portions 14 and ends 16 t of the positive electrode collectormembers 16 toward the prismatic outer can 12. With such a structurebeing employed, the protruding portion 24 t of the resin materialportion 24 p of the positive electrode intermediate member 24 will bepositioned at least one of the ends of the flattened wound electrodeassembly 11, which are positioned at the inside ends of the prismaticouter can 12, and so the risk of the ends 14 t of the two split groupsof positive electrode substrate exposed portions 14 and the ends 16 t ofthe positive electrode collector members 16 both contacting with theinside of the prismatic outer can 12 will be eliminated.

Moreover, since the protruding portion 24 t of the resin materialportion 24 p of the positive electrode intermediate member 24 protrudesbeyond the ends 14 t of the substrate exposed portions 14 and the ends16 t of the collector members 16 when inserted between the two splitgroups of positive electrode substrate exposed portions 14, the positiveelectrode intermediate member 24 can be clasped at the protrudingportion 24 t when being inserted between the two split groups ofpositive electrode substrate exposed portions 14, thereby facilitatingthe insertion.

The flattened wound electrode assembly 11 will be usually wrapped in afolded-back plate-like resin sheet 23 when inserted into the prismaticouter can 12, and thanks to the presence of the protruding portion 24 tof the resin material portion 24 p of the positive electrodeintermediate member 24, even if the resin sheet 23 is mispositioned,contacting of the ends 14 t of the positive electrode substrate exposedportions 14 and the ends 16 t of the positive electrode collectormembers 16 with the prismatic outer can 12 will be reliably suppressed.If external force should act on the prismatic sealed battery 10 anddeform the prismatic outer can 12, the possibility of the ends 14 t ofthe positive electrode substrate exposed portions 14 and the ends 16 tof the positive electrode collector members 16 contacting with theprismatic outer can 12 will be smaller than in the case where theelectrode assembly 11 is covered simply by the resin sheet 23, because,unlike the resin sheet 23, the resin material portion 24 p of thepositive electrode intermediate member 24 is a rigid body and thereforeis not likely to deform.

Furthermore, a flat portion 24 u is formed on that portion of theprotruding portion 24 t of the resin material portion 24 p of thepositive electrode intermediate member 24 that is opposed to theprismatic outer can 12, and chamfered portions 24 u′ are formed onlongitudinal angled portions of the flat portion 24 u. With such astructure provided, assembly will be easier, because by placing the flatportion 24 u of the protruding portion 24 t of the resin materialportion 24 p of the positive electrode intermediate member 24 against atleast one of the ends of the prismatic outer can 12 during insertion ofthe flattened electrode assembly 11 into the prismatic outer can 12, theelectrode assembly 11 can be inserted by being slid in. Moreover, withchamfered portions 24 u′ being formed on the longitudinal angledportions of the flat portion 24 u of the protruding portion 24 t of theresin material portion 24 p of the positive electrode intermediatemember 24, insertion into the prismatic outer can 12 will be easier, andfurthermore, even where the flattened electrode assembly 11 is wrappedin a folded-back plate-like resin sheet 23 when inserted into theprismatic outer can 12, ripping of the resin sheet 23 by the angledportions of the protruding portion 24 t of the resin material portion 24p of the positive electrode intermediate member 24 will be suppressed.

In the resin material portion 24 p of the positive electrodeintermediate member 24 that is used in the First Embodiment, chamferedportions 24 v are formed on the angled portions of the side that isinserted into the two split groups of positive electrode substrateexposed portions 14. With such a structure provided, during insertion ofthe positive electrode intermediate member 24 between the two splitgroups of stacked positive electrode substrate exposed portions 14, thechamfered portions 24 v of the positive electrode intermediate member 24will cause little damage to the positive electrode substrate exposedportions 14 if they contact them, and the positive electrode connectingconductive members 24A can be made to contact against the inner face ofthe split groups of positive electrode substrate exposed portions 14when the positive electrode intermediate member 24 is inserted betweenthe two split groups of positive electrode substrate exposed portions14.

Note that in the foregoing First Embodiment, chamfered portions 24 u′formed on the longitudinal angled portions of the flat portion 24 u ofthe protruding portion 24 t of the resin material portion 24 p of thepositive electrode intermediate member 24 were described as an example,but as a variant of that, chamfered portions 24 u″ could be formed onthe widthwise angled portions of the flat portion 24 u on the side ofthe protruding portion 24 t of the resin material portion 24 p of thepositive electrode intermediate member 24 that is opposed to the bottomof the prismatic outer can 12. With such a structure, the state when thepositive electrode intermediate member 24 has been inserted into the twosplit groups of positive electrode substrate exposed portions 14 will bethat shown in FIG. 2G, and so when, after resistance welding, theelectrode assembly 11 with the positive electrode intermediate member 24installed thereto is inserted into the prismatic outer can 12, even ifwrapped in a folded-back plate-like resin sheet 23, the electrodeassembly 11 can be inserted more smoothly into the prismatic outer can12.

Next, as shown in FIG. 3, the flattened wound electrode assembly 11,with the positive electrode collector members 16 and the positiveelectrode intermediate member 24 holding the positive electrodeconnecting conductive members 24A disposed therein, is disposed betweenpairs of resistance welding electrode rods 31 and 32 above and below,and the pairs of resistance welding electrode rods 31 and 32 are eachbrought into contact with one of the positive electrode collectormembers 16, which are disposed on the outermost two surfaces of thepositive electrode substrate exposed portions 14. Then an appropriatedegree of pressure is applied between the pairs of resistance weldingelectrode rods 31 and 32, and resistance welding is performed underparticular predetermined conditions.

In this resistance welding, the positive electrode intermediate member24 is disposed in a stably positioned state between the two split groupsof positive electrode substrate exposed portions 14, and so it ispossible, using just one set of pairs of resistance welding electroderods 31 and 32, to resistance-weld a plurality of positive electrodeconnecting conductive member 24A portions one by one, or, using multiplesets of pairs of resistance welding electrode rods 31 and 32, toresistance-weld a plurality of positive electrode connecting conductivemember 24A portions two or more at a time. With this positive electrodeintermediate member 24 being used in the First Embodiment, thedimensional precision between the connecting conductive members 24A andthe electrode rods 31 and 32 is enhanced, which means that theresistance welding can be done in an accurate and stable state, andvariation in the welding strength will be curbed.

Note that because an aperture 24 c is formed in the protrusion 24 b ofthe positive electrode connecting conductive members 24A in the FirstEmbodiment, the current will readily concentrate at the tip of theprotrusion 24 b and furthermore the tip of the protrusion 24 b willreadily bite into the positive electrode substrate exposed portions 14.Thus, the weldability is improved over the case where no aperture 24 cis formed. Moreover, the resistance welding is carried out with thepressure being applied so that the tip of the protrusion 24 b issemi-crushed and the portion of the protrusion 24 b that contacts withthe positive electrode substrate exposed portions 14 changes fromannular to circular, then it will be possible to perform the weldingmore stably.

Thus, it is preferable that, for example as shown in FIG. 4D, the shapeof the protrusion 24 b of the positive electrode connecting conductivemembers 24A be made such that the tip of the protrusion 24 b issemi-crushed and the portion of the protrusion 24 b that contacts withthe positive electrode substrate exposed portions 14 changes fromannular to circular. In such a case, a hollow 24 d will be formed in theinterior of the protrusion 24 b. This will make the portion of theprotrusion 24 b that contacts with the positive electrode substrateexposed portions 14 into a circular shape, thereby promoting theemission of heat from the center of the positive electrode connectingconductive member 24A, enabling further stabilized welding.

Note that whether the portion of the protrusion 24 b that contacts withthe positive electrode substrate exposed portions 14 is semi-crushed oris annular is known to depend mainly on the pressure applied duringwelding. The tendency is for the protrusion tip to be annular when thewelding applied pressure is weak, and to be semi-crushed when thewelding applied pressure is strong. Besides that, it is considered thatthe larger the height of the protrusion 24 b and the larger the depth ofthe aperture 24 c, the more readily will the portion be semi-crushed;when the aperture's depth is small, the tip of the protrusion 24 b willmore readily retain its annular shape and be in a condition to bite intothe substrate exposed portions.

During the resistance welding, it is preferable that the central axes ofthe pairs of resistance welding electrode rods 31 and 32 coincide withthose of the positive electrode connecting conductive members 24A, andthat the positive electrode connecting conductive members 24A be held insuch a manner that they will not come out of position due to thepressure application, etc. In addition, a semiconductor type weldingpower source using commonly-known transistors or the like can be used asthe resistance welding machine.

There follows an explanation, using FIGS. 4A to 4D, of the reasons forthe difference arising in the heat-up conditions when the portion of theprotrusion 24 b that contacts with the positive electrode substrateexposed portions 14 is annular and when it is circular. FIG. 4A is aview showing the route by which the resistance welding current flows inthe case where the portion of the protrusion 24 b that contacts with thepositive electrode substrate exposed portions 14 is annular, FIG. 4B isa view showing the portions in FIG. 4A where heat-up is intense, FIG. 4Cis a view showing the route by which the resistance welding currentflows in the case where the portion of the protrusion 24 b that contactswith the positive electrode substrate exposed portions 14 is circular,and FIG. 4D is a view showing the portions in FIG. 4C where heat-up isintense.

Since the current flows through the places with smallest resistance, theportion of the interior of the resistance welding electrode rods 31 and32 where the current flows the most is its center. In the case where theportion of the protrusion 24 b that contacts with the positive electrodesubstrate exposed portions 14 is annular, the welding current I will,for example, flow from the upper resistance welding electrode rod 31through the upper positive electrode collector member 16 and positiveelectrode substrate exposed portions 14 into the annular tip of theupper protrusion 24 b of the positive electrode connecting conductivemember 24A, where the current is split up into an annular stream, whichflows through the interior of the main body 24 a of the positiveelectrode connecting conductive member 24A and into the annular tip ofthe lower protrusion 24 b of the positive electrode connectingconductive member 24A, where the current is focused, and then flowsthough the lower positive electrode substrate exposed portions 14 andpositive electrode collector member 16 into the lower resistance weldingelectrode rod 32, as shown in FIG. 4A. Therefore, in the case where theportion of the protrusions 24 b that contacts with the positiveelectrode substrate exposed portions 14 is annular, the current will notflow in the center of the protrusions 24 b, and as a result, the weldingstart points will occur in an annular configuration, and there will bemultiple start points as shown in FIG. 4B.

By contrast, in the case where the portion of the protrusions 24 b thatcontacts with the positive electrode substrate exposed portions 14 hasbeen semi-crushed and become circular, a hollow 24 d will be formed inthe interior of the protrusion 24 b, and as a result, the weldingcurrent I will, for example, flow from the upper resistance weldingelectrode rod 31 through the upper positive electrode collector member16 and positive electrode substrate exposed portions 14 and into thecenter of the circular tip of the upper protrusion 24 b of the positiveelectrode connecting conductive member 24A, where the current is splitup into an annular stream, which flows through the interior of the mainbody 24 a of the positive electrode connecting conductive member 24A andinto the center of the circular tip of the lower protrusion 24 b of thepositive electrode connecting conductive member 24A, where the currentis focused, and then flows though the lower positive electrode substrateexposed portions 14 and positive electrode collector member 16 into thelower resistance welding electrode rod 32, as shown in FIG. 4C.

In this example, at the protrusion 24 b portion the welding current Iavoids the hollow 24 d and is split up into an annular stream, but sincethe hollow 24 d is present in the central interior of the circular tip,the heat absorption that accompanies the melting of metal is lessened,and so the area around the center of the circular tip of the protrusion24 b becomes the place that heats up most readily. Therefore, in thecase where the portion of the protrusions 24 b that contacts with thepositive electrode substrate exposed portions 14 is circular, thecurrent will be focused in the center of the circular tip of theprotrusion 24 b, and so the shape of the portion that heats up intenselydue to the welding current I will be spherical, as shown in FIG. 4D,which means that the welded state will be more stable and moreover thewelding strength will be high.

Note that the foregoing First Embodiment described an example in whichthe positive electrode connecting conductive members 24A have a columnarmain body 24 a and truncated cone-shaped protrusions 24 b in whichapertures 24 c are formed. However, with the invention it is possible touse protrusions 24 b in which no apertures are formed, or that aretruncated pyramid-shaped, more precisely, truncated triangular orquadrangular truncated pyramid-shaped, or even multiangular truncatedpyramid-shaped.

In the case where no apertures are formed in the protrusions 24 b, theeffect of the protrusions 24 b will be similar to that of the long-usedprojections during resistance welding. Even in this case, however, itwill be possible to carry out resistance welding satisfactorily betweenthe positive electrode collector member 16, the stacked plurality ofpositive electrode substrate exposed portions 14 and the positiveelectrode connecting conductive members 24A. Where the depth of theapertures 24 c formed in the protrusions 24 b is small, the effectsarising during resistance welding will gradually approach those when noapertures are formed in the protrusions 24 b.

Although an example has been described in which items having a circularmain body 24 a were used as the positive electrode connecting conductivemembers 24A, any item having the form of a metallic block, such assquare cylindrical, elliptical cylindrical, or the like shape, will besuitable, and it will further be possible to use an item in which theaperture 24 c (see FIGS. 2A to 2G) penetrates fully through the mainbody 24 a. Particularly in the case where the aperture 24 c penetratesfully through the main body 24 a, the main body 24 a of the positiveelectrode connecting conductive members 24A will be cylindrical, but insuch a case the main body 24 a can be made to also serve as protrusionsby forming the two ends thereof or leaving them projecting. In such acase where the main body 24 a of the positive electrode connectingconductive members 24A is cylindrical, it will be advisable to make thecylindrical portion thicker to a certain degree, in order to render theelectrical resistance small.

The foregoing First Embodiment described the case where the stackedplurality of positive electrode substrate exposed portions 14 are splitinto two groups and resistance welding is performed using the positiveelectrode collector members 16 and the positive electrode connectingconductive members 24A, but alternatively the positive electrodeconnecting conductive members 24A could be made to also serve aspositive electrode collector members, and be connected to the positiveelectrode terminal 17. In such a case it will suffice to employ, inplace of the positive electrode collector members used in the FirstEmbodiment, a welding receiving member constituted of thin sheetmaterial formed from the same material as the positive electrodeconnecting conductive members 24A.

Second to Fourth Embodiments

The First Embodiment described, for the positive electrode connectingconductive members 24A that are held by the positive electrodeintermediate member 24, an item in which a protrusion 24 b that is,e.g., truncated pyramid-shaped, is formed on each of two opposed faces24 e of the cylindrical columnar main body 24 a, as shown in FIGS. 2A to2C. Thus, when the main body 24 a is cylindrical columnar, angledportions 24 f will be formed between the two opposed faces 24 e and sidefaces of the cylindrical columnar main body 24 a. Therefore, as shown inFIG. 3, when the positive electrode intermediate member 24 holding thepositive electrode connecting conductive members 24A is disposed insidethe two split groups of stacked positive electrode substrate exposedportions 14, so that each of the truncated pyramid-shaped protrusions 24b on the two ends of the positive electrode connecting conductivemembers 24A contacts against the stacked positive electrode substrateexposed portions 14, then if the angled portions 24 f protrude exposedfrom the surface of the positive electrode intermediate member 24, theexposed angled portions 24 f will more readily contact with the stackedpositive electrode substrate exposed portions 14, and the positiveelectrode substrate exposed portions 14 will readily deform.

Accordingly, for the positive electrode connecting conductive member 24Bof a Second Embodiment of the invention, surfaces 24 g provided withchamfered portions are formed on the angled portions 24 f between thetwo opposed faces 24 e and side faces of the cylindrical columnar mainbody 24 a of the First Embodiment. This positive electrode connectingconductive member 24B of the Second Embodiment will now be describedusing FIG. 5A. Note that FIG. 5A is a front view of a positive electrodeconnecting conductive member 24B of the Second Embodiment.

With the positive electrode connecting conductive member 24B of theSecond Embodiment, which has surfaces 24 g provided with chamferedportions as mentioned above, even if the surfaces 24 g provided withchamfered portions protrude from the surface of the positive electrodeintermediate member 24, when the positive electrode intermediate member24 holding the positive electrode connecting conductive members 24B isdisposed inside the two split groups of stacked positive electrodesubstrate exposed portions 14, so that each of the truncated cone-shapedprotrusions 24 b on the two ends of the positive electrode connectingconductive members 24B contacts against the stacked positive electrodesubstrate exposed portions 14, little damage will be caused to thestacked positive electrode substrate exposed portions 14, and insertionas far as the position for welding to the positive electrode substrateexposed portions 14 will be easy. Hence, the weldability will beimproved.

Either curved surfaces or planes can be employed for the surfaces 24 gprovided with chamfered portions of the positive electrode connectingconductive members 24B of the Second Embodiment. However, if thesurfaces 24 g provided with chamfered portions are made into planes,then the surfaces 24 g provided with chamfered portions and the surfaceson which the protrusion 24 b is formed will, of necessity, form obtuseangles with respect to the positive electrode substrate exposed portions14, and so the positive electrode substrate exposed portions 14 and theprotrusions 24 b will readily come into contact when the positiveelectrode connecting conductive members 24B is brought into contact withthe stacked positive electrode substrate exposed portions 14, with theresult that the weldability will be improved.

As regards the positive electrode connecting conductive members 24C of aThird Embodiment of the invention, as shown in FIG. 5B, these positiveelectrode connecting conductive members 24C exhibit a form such that thesurfaces 24 g provided with chamfered portions are extended as far asthe portion where the protrusion 24 b is formed, and the faces 24 econstituted of the two mutually parallel planar faces on the main body24 a of the positive electrode connecting conductive members 24B of theSecond Embodiment are absent. These positive electrode connectingconductive members 24C of the Third Embodiment will also yield fairlygood resistance welding advantages.

However, the configuration with the two faces 24 e where the protrusion24 b is provided both being exposed, as in the positive electrodeconnecting conductive members 24B of the Second Embodiment is used, moreprecisely, the configuration whereby two mutually parallel planar facesare formed on the main body 24 a of the positive electrode connectingconductive members 24B, is more preferable, because when the pressure isapplied to the resistance welding electrode during resistance welding,the positive electrode connecting conductive members 24B will not beprone to deform, and part of the protrusion 24 b that melts and deforms,or part of the positive electrode substrate exposed portions 14 thatmelt, during resistance welding, will dwell on these surfaces 24 e andbe inhibited from flowing out toward the sides of the positive electrodeconnecting conductive members 24B, and moreover, since the faces 24 ewill be the faces that contact with the positive electrode substrateexposed portions 14, the positions of the positive electrode connectingconductive members 24B will be stabilized, and it will be possible toobtain higher-reliability resistance welds.

Furthermore, the positive electrode connecting conductive members 24D ofa Fourth Embodiment of the invention are the positive electrodeconnecting conductive members 24B of the Second Embodiment, butprovided, in the central portion of the protrusions 24 b, with apertures24 c having a depth D that is smaller than the height H of theprotrusions 24 b.

FIG. 5D is a schematic side view that illustrates resistance weldingcarried out using the positive electrode connecting conductive members24D of the Fourth Embodiment in order to show that when the surfaces 24g provided with chamfered portions are formed, as in the positiveelectrode connecting conductive members 24B to 24D of the Second toFourth Embodiments, the positive electrode intermediate member 24 canmore readily be inserted between the two split groups of positiveelectrode substrate exposed portions 14. It will be seen from FIG. 5Dthat even with the positive electrode connecting conductive members 24Dprotruding from the surface of the positive electrode intermediatemember 24, the positive electrode substrate exposed portions 14 will notbe prone to deform geometrically. FIG. 5D also illustrates the casewhere the angled portions on the side of the positive electrodeintermediate member 24 that is inserted between the positive electrodesubstrate exposed portions 14 are chamfered. It will also be seen fromFIG. 5D that due to the shape of the positive electrode intermediatemember 24, the positive electrode substrate exposed portions 14 will notbe prone to deform geometrically even when the positive electrodeintermediate member 24 is inserted between the two split groups ofpositive electrode substrate exposed portions 14.

Fifth and Sixth Embodiments

In the First to Fourth Embodiments above, examples were described inwhich the positive electrode substrate exposed portions 14 of theflattened wound electrode assembly 11 are split into two groups, one oneach side relative to the winding center portion, each such group isbundled together, positive electrode collector members 16 are placedagainst the two outermost surfaces of the positive electrode substrateexposed portions 14, a positive electrode intermediate member 24 havingpositive electrode connecting conductive members 24A, 24B, 24C or 24D isinserted between the two split groups of positive electrode substrateexposed portions 14, and resistance welding is performed by bringingpairs of resistance welding electrodes 31, 32 into contact with bothsurfaces of the positive electrode collector members 16 (see FIG. 3).However, with the present invention, it is not necessarily a necessarycondition to place positive electrode collector members 16 connected tothe positive electrode terminal 17 against both of the outermostsurfaces of the two split groups of positive electrode substrate exposedportions 14; it will suffice to perform resistance welding with positiveelectrode collector members 16 placed against at least one surface ofthe two split groups of positive electrode substrate exposed portions14.

There follows a description, using FIGS. 6A and 6B, of the post-weldingdisposition of the positive electrode connecting conductive member 24portion in Fifth and Sixth Embodiments of the invention, in which, asmentioned above, positive electrode collector members 16 connected tothe positive electrode terminal 17 are placed against at least onesurface of the two split groups of positive electrode substrate exposedportions 14. Note that FIG. 6A is a side view showing the post-weldingdisposition of the positive electrode connecting conductive member 24portion in the Fifth Embodiment, and FIG. 6B is a side view showing thepost-welding disposition of the positive electrode connecting conductivemember 24 portion in the Sixth Embodiment. The descriptions of the Fifthand Sixth Embodiments use positive electrode intermediate members 24that have the same positive electrode connecting conductive members 24Aas the items used in the First Embodiment.

In the Fifth Embodiment, as shown in FIG. 6A, a positive electrodecollector member 16 connected to the positive electrode terminal 17 isdisposed so as to contact against one outermost surface of the two splitgroups of positive electrode substrate exposed portions 14, a positiveelectrode collection receiving member 16 a is disposed so as to contactagainst the other outermost surface of the two split groups of positiveelectrode substrate exposed portions 14, and resistance welding isperformed by placing pairs of resistance welding electrodes into contactwith the positive electrode collector member 16 and the positiveelectrode collection receiving member 16 a. In this Fifth Embodiment,the positive electrode collection receiving member 16 a is not directlyconnected to the positive electrode terminal 17, but fulfills the roleof receiving one of the pairs of resistance welding electrodes duringresistance welding. Even with a structure such as in the FifthEmbodiment, substantially the same advantageous effects are yielded asin the First Embodiment, because of the projection effect possessed bythe positive electrode connecting conductive members 24A of the positiveelectrode intermediate member 24. More precisely, the collectionreceiving member 16 a yields substantially the same advantageous effectsas the positive electrode collector member 16 with regard to resistancewelding. The meaning of “collector member” as used herein includes sucha “collection receiving member”. Disposing collector members on both theoutermost surfaces of the two split groups of positive electrodesubstrate exposed portions 14 enables resistance welding to be performedin a physically stable state.

In the Sixth Embodiment, as shown in FIG. 6B, a positive electrodecollector member 16 is disposed so as to contact against one outermostsurface of the two split groups of positive electrode substrate exposedportions 14, nothing is provided on the other outermost surface of thetwo split groups of positive electrode substrate exposed portions 14,and resistance welding is performed by placing pairs of resistancewelding electrodes into contact with the positive electrode collectormember 16 and the other outermost surface of the two split groups ofpositive electrode substrate exposed portions 14. More precisely, in theSixth Embodiment, one of the pair of resistance welding electrodes isplaced directly into contact with the other outermost surface of the twosplit groups of positive electrode substrate exposed portions 14 inorder to perform resistance welding. With a configuration such as in theSixth Embodiment, fairly good resistance welding can be performedbecause of the projection effect possessed by the positive electrodeconnecting conductive members 24A of the positive electrode intermediatemember 24, but since there is a possibility of fusion occurring betweenthe resistance welding electrodes and the other outermost surface of thepositive electrode substrate exposed portions 14, it is preferable thata positive electrode collector member 16 or a collection receivingmember 16 a be disposed on the other outermost surface of the positiveelectrode substrate exposed portions 14, as in the First to FifthEmbodiments.

Seventh to Tenth Embodiments

In the First Embodiment, an example was described that used a positiveelectrode intermediate member 24 made of synthetic resin and having arectangular parallelepiped shape. However, since any shape that can holdthe connecting conductive members 24A stably can be used to implementthe invention, the shape of the positive electrode intermediate member24 is not limited to a rectangular parallelepiped. For example, cutoutportions 24X could be formed in between the positive electrodeconnecting conductive members 24A as in the positive electrodeintermediate member 24 ₁ of a Seventh Embodiment of the invention shownin FIG. 7A, or through holes 24Yy could be formed longitudinally as inthe positive electrode intermediate member 24 ₂ of an Eighth Embodimentof the invention shown in FIG. 7B, or apertures 24Z could be formed inbetween the positive electrode connecting conductive members 24A as inthe positive electrode intermediate member 24 ₃ of a Ninth Embodiment ofthe invention shown in FIG. 7C. If such structures are employed, thecutout portions 24X, through holes 24Y, apertures 24Z, or the like willact as gas venting routes, so that any gas that may be generated in theelectrode assembly interior if abnormality occurs in the battery caneasily be expelled to the exterior of the electrode assembly, and sincethe pressure-reduction type current interruption mechanism, gas exhaustvalve, and so forth, with which a prismatic sealed battery is normallyequipped will be activated stably, safety can be secured, and ahigh-reliability prismatic sealed secondary battery can be manufactured.

Tenth Embodiment

The positive electrode connecting conductive members 24E of a TenthEmbodiment of the invention will now be described using FIGS. 8A to 8D.Note that FIG. 8A is a front view of a positive electrode connectingconductive member in the Tenth Embodiment, FIG. 8B is a longitudinalsectional view through FIG. 8A, FIG. 8C is a top view of a ring-shapedinsulating seal material, and FIG. 8D is a longitudinal sectional viewof the positive electrode intermediate member in the Tenth Embodiment.

The positive electrode connecting conductive members 24E of the TenthEmbodiment is the positive electrode connecting conductive members 24Bof the Second Embodiment shown in FIG. 8A, but with the insulating sealmaterial 26, which is formed from ring-shaped insulative thermallymelt-bonding resin, disposed around the truncated cone-shaped protrusion24 b. The height of this insulating seal material 26 is smaller than theheight H of the truncated cone-shaped protrusion 24 b.

The surfaces 24 g provided with chamfered portions are formed in thepositive electrode connecting conductive members 24E of the TenthEmbodiment, and so when the positive electrode connecting conductivemembers 24E are disposed inside the two split groups of stacked positiveelectrode substrate exposed portions 14 so that each of the truncatedcone-shaped protrusions 24 b on the two ends of the positive electrodeconnecting conductive members 24E contacts against the stacked positiveelectrode substrate exposed portions 14, little damage will be caused tothe stacked positive electrode substrate exposed portions 14, andinsertion as far as the position for welding to the positive electrodesubstrate exposed portions 14 will be easy. Hence, the weldability willbe improved.

In the positive electrode connecting conductive members 24E of the TenthEmbodiment, insulating seal materials 26 which are formed fromring-shaped insulative thermally melt-bonding resin are disposed aroundthe truncated cone-shaped protrusions 24 b on the two ends. Duringresistance welding, the stacked positive electrode substrate exposedportions 14 are pushed by the resistance welding electrodes toward thepositive electrode connecting conductive members 24E, and so theprotrusions 24 b of the positive electrode connecting conductive members24E bite into the stacked positive electrode substrate exposed portions14, thus contacting with the stacked positive electrode substrateexposed portions 14. With insulating seal materials 26 disposed in aring shape around the protrusions 24 b of the positive electrodeconnecting conductive members 24E as mentioned above, any spatteredhigh-temperature dust that may occur during resistance welding can beblocked by the insulating seal materials 26 and captured in the interiorof the insulating seal materials 26 or between the protrusions 24 b andthe insulating seal materials 26.

Moreover, in the positive electrode connecting conductive members 24E ofthe Tenth Embodiment, because the insulating seal materials 26 areformed from insulative thermally melt-bonding resin, any spatteredhigh-temperature dust that occurs during resistance welding willpartially melt the solid insulative thermally melt-bonding resin andthereby be deprived of heat, rapidly cool, and fall in temperature, withthe result that it will easily be captured inside the insulating sealmaterials 26 constituted of solid insulative thermally melt-bondingresin. Note that since, during resistance welding, the duration forwhich the current is passed is short and moreover the area over whichthe current flows is narrow, it will seldom occur that all of theinsulating seal materials 26 constituted of insulative thermallymelt-bonding resin will melt at the same time. Therefore, it will seldomoccur that spattered dust that occurs during resistance welding willdisperse from the insulating seal materials 26 and enter into theinterior of the flattened electrode assembly. Hence, a sealed batterycan be obtained that has lower occurrence of internal short-circuits andhigher reliability.

Note that the insulative thermally melt-bonding resin will preferablyhave a melting temperature of 70 to 150° C. and dissolving temperatureof 200° C. or higher, and will preferably further have chemicalresistance with regard to electrolyte and the like. For example, arubber-based seal material, acid-denatured polypropylene, orpolyolefin-based thermally melt-bonding resin may be used. Furthermore,the insulating seal material may be insulating tape with adhesive, forwhich polyimide tape, polypropylene tape, polyphenylene sulfide tape, orthe like can be used. Moreover, the whole material may consist ofinsulative thermally melt-bonding resin, or it may have a multilayerstructure that includes insulative thermally melt-bonding resin layers.

Note that although the descriptions of the First to Tenth Embodimentsabove concerned the positive electrode part, the negative electrode partemploys the same structure—except for different physical properties ofthe materials of the negative electrode substrate exposed portions 15,negative electrode collector members 18, negative electrode intermediatemember 25, negative electrode connecting conductive members 25A, andnegative electrode collection receiving member (not shown in thefigures), and therefore, yields substantially the same effects andadvantages. Furthermore, the invention does not necessarily have to beemployed in both the positive electrode part and the negative electrodepart, and may be applied to the positive electrode part alone or to thenegative electrode part alone.

In the manufacture of a sealed battery of the invention it is possibleto use positive electrode connecting conductive members and negativeelectrode connecting conductive members with protrusions of differingshapes. Differing metallic materials are used for the positive electrodesubstrates and the negative electrode substrates of an ordinary sealedbattery. For example, in a lithium ion secondary battery, aluminum oraluminum alloy is used for the positive electrode substrates and copperor copper alloy is used for the negative electrode substrates. Becausecopper and copper alloy have low electrical resistance compared withaluminum and aluminum alloy, it is more difficult to resistance-weld thenegative electrode substrate exposed portions than to resistance-weldthe positive electrode substrate exposed portions, and hard-to-meltportions are prone to occur in the stacked negative electrode substrateexposed portion interior.

In such a case, it will be desirable, in order to concentrate theelectric current and render the resistance welding easy to perform, touse protrusions with apertures formed therein for the shape of theprotrusions of the negative electrode connecting conductive members thatare used between the negative electrode substrate exposed portions,while for the shape of the protrusions of the positive electrodeconnecting conductive members that are used between the positiveelectrode substrate exposed portions, it will be desirable to useprotrusions without apertures formed therein, so that the resistancewelding will proceed easily and the positive electrode connectingconductive members will be less liable to deform.

The foregoing embodiments and figures set forth examples in which, forsimplicity of description, welding is carried out using one intermediatemember, which holds two connecting conductive members, for the substrateexposed portions of each electrode. However, the number of connectingconductive members can of course be one or three or more, and can bedetermined appropriately in accordance with the size, required output,and other characteristics of the battery.

What is claimed is:
 1. A prismatic sealed secondary battery comprising:a positive electrode plate; a negative electrode plate; a separatorinterposed between the positive electrode plate and the negativeelectrode plate; a first group of positive electrode substrate exposedportions; a second group of positive electrode substrate exposedportions; negative electrode substrate exposed portions; a resinmaterial disposed between the first group of positive electrodesubstrate exposed portions and the second group of positive electrodesubstrate exposed portions; a positive collector member that iselectrically joined to the first group of positive electrode substrateexposed portions and the second group of positive electrode exposedportions; a negative collector member that is electrically joined to thenegative electrode substrate exposed portions; a prismatic outer canincluding a mouth portion, a bottom, a first side surface, and a secondside surface; and a sealing plate sealing the mouth portion of theprismatic outer can; wherein the prismatic outer can accommodates thepositive electrode plate, the negative electrode plate, the separator,the first group of positive electrode substrate exposed portions, thesecond group of positive electrode substrate exposed portions, and thenegative electrode substrate exposed portions; wherein the first sidesurface of the prismatic outer can is perpendicular to the bottom of theprismatic outer can; wherein the second side surface of the prismaticouter can is perpendicular to the bottom of the prismatic outer can;wherein the first side surface of the prismatic outer can and the secondside surface of the prismatic outer can are parallel to each other;wherein the first group of positive electrode substrate exposed portionsand the second group of positive electrode substrate exposed portionsare arranged on the first side surface side of the prismatic outer can;wherein the negative electrode substrate exposed portions are arrangedon the second side surface side of the prismatic outer can; wherein adistance from the first side surface of the prismatic outer can to aportion of the resin material which is nearest to the first side surfaceof the prismatic outer can is less than a distance from the first sidesurface of the prismatic outer can to a portion of the first group ofpositive electrode substrate exposed portions which is nearest to thefirst side surface of the prismatic outer can; wherein the distance fromthe first side surface of the prismatic outer can to the portion of theresin material which is nearest to the first side surface of theprismatic outer can is less than a distance from the first side surfaceof the prismatic outer can to a portion of the second group of positiveelectrode substrate exposed portions which is nearest to the first sidesurface of the prismatic outer can; and wherein the distance from thefirst side surface of the prismatic outer can to the portion of theresin material which is nearest to the first side surface of theprismatic outer can is less than a distance from the first side surfaceof the prismatic outer can to a portion of the positive collector memberwhich is nearest to the first side surface of the prismatic outer can.2. The prismatic sealed secondary battery according to claim 1, whereinthe positive collector member is a folded-metal sheet joined to thefirst group of positive electrode substrate exposed portions by welding;and wherein the positive collector member is in physical direct contactwith the first group of positive electrode substrate exposed portions ata region in which the positive collector member and the first group ofpositive electrode substrate exposed portions are welded together. 3.The prismatic sealed secondary battery according to claim 2, furthercomprising a positive electrode terminal, wherein the sealing plate hasa through-hole, and wherein the positive electrode terminal passesthrough the sealing plate at the through-hole and the positive electrodeterminal is in physical direct contact with the positive collectormember.
 4. The prismatic sealed secondary battery according to claim 1,wherein a distance from the first side surface of the prismatic outercan to a portion of the resin material which is farthest from the firstside surface of the prismatic outer can is less than a distance from thefirst side surface of the prismatic outer can to a portion of the firstgroup of positive electrode substrate exposed portions and the secondgroup of positive electrode substrate exposed portions which is farthestfrom the first side surface of the prismatic outer can.
 5. The prismaticsealed secondary battery according to claim 1, wherein an insulatingresin sheet is disposed between the resin material and the first sidesurface of the prismatic outer can, and wherein the insulating resinsheet is not integral with the resin material.
 6. The prismatic sealedsecondary battery according to claim 1, wherein the resin material has athrough hole.
 7. The prismatic sealed secondary battery according toclaim 1, wherein the resin material has a cutout portion.
 8. Theprismatic sealed secondary battery according to claim 1, wherein theresin material has an aperture.
 9. The prismatic sealed secondarybattery according to claim 1, wherein the resin material is directlycontacted with both of the first group of positive electrode substrateexposed portions and the second group of positive electrode substrateexposed portions.
 10. A prismatic sealed secondary battery comprising: apositive electrode plate; a negative electrode plate; a separatorinterposed between the positive electrode plate and the negativeelectrode plate; a first group of negative electrode substrate exposedportions; a second group of negative electrode substrate exposedportions; positive electrode substrate exposed portions; a resinmaterial disposed between the first group of negative electrodesubstrate exposed portions and the second group of negative electrodesubstrate exposed portions; a positive collector member that iselectrically joined to the positive electrode substrate exposedportions; a negative collector member that is electrically joined to thefirst group of negative electrode substrate exposed portions and thesecond group of negative electrode substrate exposed portions; aprismatic outer can including a mouth portion, a bottom, a first sidesurface, and a second side surface; and a sealing plate sealing themouth portion of the prismatic outer can; wherein the prismatic outercan accommodates the positive electrode plate, the negative electrodeplate, the separator, the first group of negative electrode substrateexposed portions, the second group of negative electrode substrateexposed portions, and the positive electrode substrate exposed portions,wherein the first side surface of the prismatic outer can isperpendicular to the bottom of the prismatic outer can; wherein thesecond side surface of the prismatic outer can is perpendicular to thebottom of the prismatic outer can; wherein the first side surface of theprismatic outer can and the second side surface of the prismatic outercan are parallel to each other; wherein the first group of negativeelectrode substrate exposed portions and the second group of negativeelectrode substrate exposed portions are arranged on the first sidesurface side of the prismatic outer can; wherein the positive electrodesubstrate exposed portions are arranged on the second side surface sideof the prismatic outer can; wherein a distance from the first sidesurface of the prismatic outer can to a portion of the resin materialwhich is nearest to the first side surface of the prismatic outer can isless than a distance from the first side surface of the prismatic outercan to a portion of the first group of negative electrode substrateexposed portions which is nearest to the first side surface of theprismatic outer can; wherein the distance from the first side surface ofthe prismatic outer can to the portion of the resin material which isnearest to the first side surface of the prismatic outer can is lessthan a distance from the first side surface of the prismatic outer canto a portion of the second group of negative electrode substrate exposedportions which is nearest to the first side surface of the prismaticouter can; wherein the distance from the first side surface of theprismatic outer can to the portion of the resin material which isnearest to the first side surface of the prismatic outer can is lessthan a distance from the first side surface of the prismatic outer canto a portion of the negative collector member which is nearest to thefirst side surface of the prismatic outer can.
 11. The prismatic sealedsecondary battery according to claim 10, wherein the negative collectormember is a folded-metal sheet joined to the first group of negativeelectrode substrate exposed portions by welding; and wherein thenegative collector member is in physical direct contact with the firstgroup of negative electrode substrate exposed portions at a region inwhich the negative collector member and the first group of negativeelectrode substrate exposed portions are welded together.
 12. Theprismatic sealed secondary battery according to claim 11, furthercomprising a negative electrode terminal, wherein the sealing plate hasa through-hole, and wherein the negative electrode terminal passesthrough the sealing plate at the through-hole and the negative electrodeterminal is in physical direct contact with the negative collectormember.
 13. The prismatic sealed secondary battery according to claim10, wherein a distance from the first side surface of the prismaticouter can to a portion of the resin material which is farthest from thefirst side surface of the prismatic outer can is less than a distancefrom the first side surface of the prismatic outer can to a portion ofthe first group of negative electrode substrate exposed portions and thesecond group of negative electrode substrate exposed portions which isfarthest from the first side surface of the prismatic outer can.
 14. Theprismatic sealed secondary battery according to claim 10, wherein aninsulating resin sheet is disposed between the resin material and thefirst side surface of the prismatic outer can, and wherein theinsulating resin sheet is not integral with the resin material.
 15. Theprismatic sealed secondary battery according to claim 10, wherein theresin material has a through hole.
 16. The prismatic sealed secondarybattery according to claim 10, wherein the resin material has a cutoutportion.
 17. The prismatic sealed secondary battery according to claim10, wherein the resin material has an aperture.
 18. The prismatic sealedsecondary battery according to claim 10, wherein the resin material isdirectly contacted with both of the first group of negative electrodesubstrate exposed portions and the second group of negative electrodesubstrate exposed portions.